Date of Award

5-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Matthew L. Gorring

Committee Member

Gregory A. Pope

Committee Member

Joshua C. Galster

Abstract

The Cortlandt-Beemerville magmatic belt of probable late Ordovician age is bound in the west by the Beemerville alkaline complex, New Jersey, and in the east by the calc-alkalic to alkalic Cortlandt complex, New York. Connecting the Cortlandt and Beemerville plutonic complexes is a string of east-west trending lamprophyre and felsic dike rocks (Eby, 2004). The Stony Point complex on the western side of the Hudson River is linked to the Cortlandt complex on the eastern side of the river, as well as the Rosetown complex further to the west through similar mineralogical and chemical compositions. Due to a lack of deformation, both complexes are hypothesized to have been intruded after the Taconic Orogeny had ceased (Ratcliffe, 1968), and is further supported by a Sm-Nd isochron age of 430 ± 34 Ma as the crystallization age of the Cortlandt Complex (Domenick and Basu, 1982). Both complexes contain exposures of diorite and cortlandtite. The latest geochemistry performed by Bender et al. (1984) indicates that the Cortlandt diorite as well as the majority of the other Cortlandt plutons could have originated from a single alkali basalt parent magma through one or all of the processes of crystal fractionation, accumulation, and crustal contamination. However, a genetic link between the diorite of Stony Point and the proposed alkali basalt parent could not be determined (Bender, 1984).

Forward modeling using the Rayleigh Fractionation method for trace element modeling (Winter, 2001), as well as major element modeling using a least squares mixing model (Bryan et al., 1969) show a plausible connection between the Stony Point diorite and the proposed parental source through the use of a two-stage model. The proposed parental source for the diorite at Stony Point is Bender et al.'s (1984) alkali basalt (40P) that had been used to model the majority of the Cortlandt complex. The most realistic model calls for approximately 60-65% of the parental material (40P) to be removed via the crystal fractionation of: olivine (2-3%), clinopyroxene (41-42%), garnet (11-16%), amphibole (27-31%), and plagioclase (9-17%), followed by the addition of about 25-30% cumulate plagioclase of an andesine type composition.

File Format

PDF

Download

Share

COinS